Plasma processing apparatus and cleaning method

ABSTRACT

Disclosed is a plasma processing apparatus including: a processing container; a susceptor configured to serve as a lower electrode and mount a processing target substrate thereon; a shower head provided above the susceptor to supply a processing gas into the processing container; an upper electrode provided above the placing table; a high frequency power supply configured to apply a high frequency power to the susceptor to generate plasma of the processing gas within the processing container; and a DC voltage application unit configured to apply a DC voltage to the upper electrode. The shower head includes a UEL base, and a CEL provided on the UEL base at susceptor side, and an insulating portion provided between the UEL base and the CEL. The DC power supply applies the DC voltage to the CEL.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority from Japanese PatentApplication No. 2014-117030, filed on Jun. 5, 2014, with the JapanPatent Office, the disclosure of which is incorporated herein in itsentirety by reference.

TECHNICAL FIELD

Various aspects and exemplary embodiments of the present disclosure arerelated to a plasma processing apparatus and a cleaning method.

BACKGROUND

There is known a plasma processing apparatus that is provided with aprocessing container, an upper electrode provided within the processingcontainer, and a lower electrode provided within the processingcontainer and connected to a high frequency power supply. In such aplasma processing apparatus, a semiconductor wafer is mounted on thelower electrode, a processing gas is supplied into the processingcontainer, and a high frequency power is applied to the lower electrode.Then, the processing gas within the processing container is turned intoplasma by the high frequency power supplied into the processingcontainer through the lower electrode so that, for example, ions, aregenerated, and a plasma processing such as, for example, an etchingprocessing, is performed on the semiconductor wafer by, for example, theions.

In the plasma processing apparatus, a reaction product produced from theprocessing gas containing a reaction gas is adhered to, for example, aside wall of the processing container or the upper electrode. When thereaction product attached to the side wall or the upper electrode ispeeled off from the side wall or the upper electrode to form particlesand the particles float within the processing container, some of theparticles may be attached to the semiconductor wafer. The particles maycause a defect on, for example, a semiconductor device manufactured fromthe semiconductor wafer. Accordingly, it is necessary to remove thereaction product adhered within the processing container.

For example, there is known a cleaning method in which a negative directcurrent voltage is applied to the upper electrode and oxygen gas isintroduced into the processing container so that oxygen ions and oxygenradicals are generated from the oxygen gas by the high frequency powerapplied to the lower electrode to cause the reaction product adhered tothe upper electrode to react with either the oxygen ions or the oxygenradicals to be removed from the upper electrode.

SUMMARY

A plasma processing apparatus according to an aspect of the presentdisclosure includes: a processing container; a gas supply unitconfigured to supply a processing gas into the processing container; aplacing table configured to serve as a lower electrode and mount aprocessing target substrate thereon; an upper electrode provided abovethe placing table; a plasma generation unit configured to generateplasma of the processing gas within the processing container by applyinghigh frequency power to the placing table; and a direct current (DC)voltage application unit configured to apply a DC voltage to the upperelectrode. The upper electrode includes a base member, a cover memberprovided on the base member at a side of the placing table, and aninsulating portion provided between the base member and the cover memberso as to insulate the base member and the cover member. The DC voltageapplication unit applies the DC voltage to the cover member.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view illustrating an exemplaryplasma processing apparatus according to an exemplary embodiment.

FIG. 2 is an enlarged cross-sectional view illustrating an exemplaryshower head.

FIG. 3 is a schematic diagram illustrating an exemplary configuration ofa conventional DRM type plasma processing apparatus.

FIG. 4 is a schematic diagram illustrating an exemplary configuration ofa DRM type plasma processing apparatus in which DCS (Direct CurrentSuperposition) is incorporated.

FIG. 5 is a schematic diagram illustrating an exemplary configuration ofa plasma processing apparatus according to an exemplary embodiment ofthe present disclosure.

FIG. 6 is an enlarged cross-sectional view illustrating an exemplaryshape of a UEL (Upper ELectrode) base.

FIG. 7 is an enlarged cross-sectional view illustrating an exemplaryshape of a vicinity of an opening of the UEL base.

FIG. 8 is an enlarged cross-sectional view illustrating an exemplaryshape of a recess, in which a seal material is disposed.

FIG. 9 is an enlarged cross-sectional view illustrating an exemplaryshape of a screw hole.

FIG. 10 is an enlarged cross-sectional view illustrating an exemplaryshape of a protrusion of the UEL base.

FIG. 11 is a view illustrating an exemplary shape of a test piece.

FIG. 12 is an explanatory view for describing an exemplary configurationof a test.

FIG. 13 is a view representing an exemplary test result of awithstanding voltage.

FIG. 14 is a view representing an exemplary test result of a removalrate of an adhered product in relation to a DC voltage applied to a CEL(Cover Electrode).

FIG. 15 is a flowchart illustrating an exemplary cleaning sequence ofthe CEL.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawing, which form a part hereof. The illustrativeembodiments described in the detailed description, drawing, and claimsare not meant to be limiting. Other embodiments may be utilized, andother changes may be made without departing from the spirit or scope ofthe subject matter presented here.

In the above-described plasma processing apparatus that does not have acleaning function, it is necessary to remove the reaction productadhered to the upper electrode by taking out and cleaning the upperelectrode from the processing container. In order to improve thethroughput of a process while preventing the pollution caused byparticles, it is considered to add the cleaning function as describedabove to the plasma processing apparatus.

When the cleaning function as described above is added, the environmentwithin the plasma processing apparatus may be changed from theenvironment of the process that has been performed until now. Forexample, the potential of the upper electrode with respect to the lowerelectrode may be changed as compared to that before the addition of thecleaning function in some cases.

Some plasma processing apparatuses are operated using a processingrecipe established by repeating fine adjustments for various parametersover many years. In such plasma processing apparatuses, when theenvironment therein is changed, the processing recipe establishedthrough the adjustments up to now cannot be applied. For that reason, itis necessary to finely adjust various parameters in order to reproduceprocess characteristics which have been implemented by a combination ofa plasma processing apparatus and a processing recipe which has beenused up to now.

A plasma processing apparatus disclosed herein includes: a processingcontainer; a gas supply unit configured to supply a processing gas intothe processing container; a placing table configured to serve as a lowerelectrode and mount a processing target substrate thereon; an upperelectrode provided above the placing table; a plasma generation unitconfigured to generate plasma of the processing gas within theprocessing container by applying high frequency power to the placingtable; and a DC voltage application unit configured to apply a DCvoltage to the upper electrode. The upper electrode includes a basemember, a cover member provided on the base member at a side of theplacing table, and an insulating portion provided between the basemember and the cover member so as to insulate the base member and thecover member. The DC voltage application unit applies the DC voltage tothe cover member.

In one exemplary embodiment of the plasma processing apparatus disclosedherein, the insulating portion may be an insulative coating formed on asurface of the base member.

In one exemplary embodiment of the plasma processing apparatus disclosedherein, the base member may be formed of aluminum, and the insulatingportion may be an anodic oxide coating formed on the surface of the basemember.

In one exemplary embodiment of the plasma processing apparatus disclosedherein, a radius of a protruding corner rounding formed on the placingtable side surface of the base member may be in a range of 0.2 mm ormore and 1.0 mm or less.

In one exemplary embodiment of the plasma processing apparatus disclosedherein, a withstanding voltage of the insulating portion may be 730 V orless.

In one exemplary embodiment of the plasma processing apparatus disclosedherein, the DC voltage application unit may apply a voltage in a rangeof more than −730 V and −150 V or less to the cover member.

A cleaning method disclosed herein includes: supplying a processing gasinto a processing container; applying a DC voltage to an upper electrodewithin the processing container; and generating plasma of the processinggas within the processing container by applying a high frequency powerto a placing table on which a processing target substrate is mounted.When applying the DC voltage, the DC voltage is applied to a cover platein the upper electrode that includes a base plate, the cover plateprovided on the base plate at a side of the placing table, and aninsulating part provided between the base plate and the cover plate toinsulate the base plate and the cover plate.

According to various aspects and exemplary embodiments of the presentdisclosure, it is enabled to achieve a plasma processing apparatus and acleaning method, in which an effect according to addition of a cleaningfunction to an existing plasma processing apparatus on a process may besuppressed to be low.

Hereinafter, exemplary embodiments of a plasma processing apparatus anda cleaning method disclosed herein will be described in detail withreference to the accompanying drawings. The present disclosure is notlimited to the exemplary embodiments disclosed herein. In addition,respective exemplary embodiments may be properly combined with eachother without conflicting processing contents.

[Configuration of Plasma Processing Apparatus 10]

FIG. 1 is a vertical cross-sectional view illustrating an exemplaryplasma processing apparatus 10 according to an exemplary embodiment. Theplasma processing apparatus 10 in the present exemplary embodiment isconfigured as a DRM (Dipole Ring Magnet) type plasma processingapparatus. The plasma processing apparatus 10 in the present exemplaryembodiment may be used for an etching or CVD (Chemical Vapor Deposition)using plasma, for example. The plasma processing apparatus 10illustrated in FIG. 1 includes a cylindrical processing container 11.The processing container 11 is electrically grounded. The processingcontainer 11 has a processing space S therein. Within the processingcontainer 11, a cylindrical susceptor 12 is disposed as a placing tableon which a wafer is mounted as a processing target substrate.

The inner wall surface of the processing container 11 is covered by aside wall member 45. The side wall member 45 is formed of, for example,aluminum, and a surface thereof facing the processing space S is coatedwith, for example, yttria (Y₂O₃). The susceptor 12 is installed on thebottom portion of the processing container 11 with an insulative member29 interposed therebetween. A side surface of the susceptor 12 iscovered with a susceptor side surface covering member 120.

The inner wall of the processing container 11 and the side surface ofthe susceptor 12 form an exhaust path 13 serving as a flow path thatdischarges gas molecules above the susceptor 12 to the outside of theprocessing container 11. In the midway of the exhaust path 13, anannular baffle plate 14 is disposed so as to prevent leakage of plasma.In addition, the space downstream of the baffle plate 14 in the exhaustpath 13 extends around the lower side of the susceptor 12 to communicatewith an APC (Adaptive Pressure Control) valve 15 that is a variablebutterfly valve. The APC valve 15 is connected to a TMP (Turbo MolecularPump) 17 serving as an exhaust pump for a vacuum processing via anisolator 16, and the TMP 17 is connected to a DP (Dry Pump) 18 servingas an exhaust pump via a valve V1.

An exhaust flow path formed by the APC valve 15, the isolator 16, theTMP 17, the valve V1 and the DP 18 performs a pressure control of theinterior of the processing container 11, more specifically theprocessing space S by the APC valve 15. Furthermore, the exhaust flowpath decompresses the interior of the processing container 11 tosubstantially a vacuum state by the TMP 17 and the DP 18.

In addition, a pipe 19 is connected between the APC valve 15 and theisolator 16, and the pipe 19 is connected to the DP 18 via a valve V2.The pipe 19 and the valve V2 bypass the TMP 17, and the interior of theprocessing container 11 is roughly evacuated by the DP 18.

A high frequency power supply 20 is connected to the susceptor 12 via apower feeding rod 21 and a matcher 22, and the high frequency powersupply 20 supplies a high frequency power of, for example, 13.56 MHz tothe susceptor 12. Thus, the susceptor 12 serves as a lower electrode. Inaddition, the matcher 22 reduces reflection of the high frequency powerfrom the susceptor 12 to the high frequency power supply 20, therebymaximizing the supply efficiency of the high frequency power to thesusceptor 12. The susceptor 12 applies the high frequency power of 13.56MHz supplied from the high frequency power supply 20, to the processingspace S.

At the upper side of the interior of the susceptor 12, a disc-shaped ECS(Electro-Static Chuck) electrode plate 23 formed of a conductive film isdisposed. A DC power supply 24 is electrically connected to the ESCelectrode plate 23. The wafer W is attracted to and held on the topsurface of the susceptor 12 by a Coulomb force or a Johnson-Rahbek forcegenerated by the DC voltage applied to the ESC electrode plate 23 fromthe DC power supply 24.

In addition, above the susceptor 12, an annular focus ring 25 isprovided to surround the periphery of the wafer W attracted to and heldon the top surface of the susceptor 12. The focus ring 25 is exposed tothe processing space S so as to converge the plasma in the processingspace S toward the surface of the wafer W so that the efficiency of areactive ion etching (RIE) processing or an ashing processing isimproved.

Within the susceptor 12, an annular coolant chamber 26 is provided toextend, for example, in the circumferential direction. A coolant suchas, for example, cooling water having a predetermined temperature, iscirculated and supplied to the coolant chamber 26 from a chiller unit(not illustrated) via a coolant pipe 27. The processing temperature ofthe wafer W attracted to and held on the top surface of the susceptor 12is controlled by the temperature of the coolant.

On the top surface of the susceptor 12 where the wafer W is attracted toand held (hereinafter, referred to as an “attraction surface”), aplurality of gas supply holes 28 are provided. The plurality of gassupply holes 28 are connected to the gas supply unit 32 via a gas supplyline 30 disposed inside the susceptor 12. The gas supply unit 32supplies a heat transfer gas such as, for example, helium gas, to a gapbetween the attraction surface of the susceptor 12 and the rear surfaceof the wafer W through the gas supply holes 28.

A plurality of pusher pins 33 are arranged in the attraction surface ofthe susceptor 12 to serve as lift pins capable of protruding from thetop surface of the susceptor 12. The pusher pins 33 are connected with amotor (not illustrated) through a ball screw, and are capable ofprotruding from the attraction surface due to the rotary motion of themotor which is converted into a rectilinear motion. When the wafer W isattracted to and held on the attraction surface so as to perform the RIEprocessing or the ashing processing on the wafer W, the pusher pins 33are accommodated in the susceptor 12. In addition, when the wafer W iscarried out from processing container 11 after the RIE processing or theashing processing is performed on the wafer W, the pusher pins 33protrude from the top surface of the susceptor 12 to separate the waferW from the susceptor 12 and lift the wafer W upwardly.

On the ceiling portion of the processing container 11, a shower head 34is disposed to face the susceptor 12. The shower head 34 includes a UEL(Upper ELectrode) 35, a UEL base 36, and a CEL (Cover ELectrode) 37. Theshower head 34 is an example of the gas supply unit and the upperelectrode. The UEL 35 is provided above the UEL base 36. The CEL 37 isformed in, for example, a disc shape, from a conductive material suchas, for example, silicon. The CEL 37 is provided below the UEL base 36and supported by the UEL base 36 from the upper side. The bottom surfaceof the CEL 37 is exposed to the processing space S, and the CEL 37suppresses the reaction product generated by the plasma of theprocessing gas supplied to the processing space S from being adhered tothe UEL base 36.

The UEL 35 and the UEL base 36 are formed of a conductive material suchas, for example, aluminum. The UEL 35 and the UEL base 36 areelectrically connected with each other, and grounded via the processingcontainer 11. In the bottom surface of the UEL base 36, an insulativemember is provided on the area where the CEL 37 is disposed. In thepresent exemplary embodiment, the insulative member provided on thebottom surface of the UEL base 36 is an anodic oxidation coating(alumite coating) formed on the bottom surface of the UEL base 36 by ananodic oxidation treatment. Thus, the UEL base 36 and the CEL 37 areelectrically insulated from each other. The UEL base 36 is an example ofthe base member.

A buffer chamber 40 is provided between the UEL 35 and the UEL base 36.The UEL base 36 is formed with a plurality of gas holes 360, each ofwhich is communicated with the buffer chamber 40. In addition, the CEL37 is formed with a plurality of gas holes 370. One end of each gas hole370 is communicated with one of the gas holes 360 of the UEL base 36,and the other end is communicated with the processing space S.

A gas introduction tube 41 is connected to the buffer chamber 40. A gassupply source 420 serving as a processing gas supply source is connectedto the gas introduction tube 41 through the insulating member 42. Theprocessing gas supplied from the gas supply source 420 is supplied tothe buffer chamber 40 through the insulating member 42 and the gasintroduction tube 41, and ejected to the processing space S through eachof the gas holes 360 and 370.

The CEL 37 is connected to a connection cable 47 via a conductiveconnection member 51 formed of, for example, aluminum. The connectioncable 47 is connected to a DC current power supply 49 through a filter48 that blocks high frequency waves. The DC power supply 49 supplies,for example, a negative DC voltage to the CEL 37 via the filter 48, theconnection cable 47, and the connection member 51. In addition, aninsulating member 50 is provided between the connection member 51 andthe UEL base 36 so that the connection member 51 and the UEL base 36 areinsulated from each other. In addition, in the connection member 51, thesurface which is in contact with the UEL 35 is subjected to the alumitetreatment so that the connection member 51 and the UEL base 36 areinsulated from each other.

In addition, an opening 43 for carrying-in/out a wafer W is provided inthe inner wall of the processing container 11 at a position thatcorresponds to the height of the wafer W lifted upwardly from thesusceptor 12 by the pusher pins. A gate valve 44 is provided on theopening 43 to open/close the opening 43.

In addition, a pair of upper and lower annular or concentric DRMs(Dipole Ring Magnets) 46 are mounted on the outer circumference of theside wall of the processing container 11. By the DRMs 46, a magneticfield in the in-plane direction of the wafer W is formed in theprocessing space S within the processing container 11.

Within the processing container 11 of the plasma processing apparatus10, the magnetic field is formed in the processing space S between thesusceptor 12 serving as the lower electrode and the shower head 34serving as the upper electrode by the DRMs 46. In addition, when thehigh frequency power is applied from the high frequency power supply 20through the susceptor 12, magnetron discharge occurs in the processingspace S. Thus, the processing gas supplied from the shower head 34 isdissociated and turned into plasma so that, for example, ions orradicals are generated. In addition, by the generated ions or radicals,a plasma processing such as, for example, an RIE, is performed on thewafer W placed on the susceptor 12. The high frequency power supply 20is an example of a plasma generation unit.

In addition, the operation of each component of the above-describedplasma processing apparatus 10 is controlled by a CPU of a control unit(not illustrated) provided in the plasma processing apparatus 10,according to program corresponding to a plasma processing such as, forexample, an RIE.

In the above-mentioned plasma processing apparatus 10, the plasmaprocessing such as, for example, an RIE, is performed on the wafer W,and, at this time, the reaction product produced from the processing gasis adhered to, for example, the bottom surface of the CEL 37. Theadhered reaction product causes particle pollution on the wafer W in aprocessing performed thereafter. For that reason, in order to remove thereaction product adhered to, for example, the bottom surface of the CEL37, a cleaning processing is performed as follows.

In the cleaning processing, for example, oxygen gas is supplied into theprocessing space S from the shower head 34, and a high frequency powerof, for example, 13.56 MHz, is applied to the processing space Ssupplied with the oxygen gas, from the susceptor 12. In the processingspace S, for example, oxygen ions or oxygen radicals are generated bythe high frequency power. For example, the oxygen ions or oxygenradicals react with the reaction product adhered to, for example, thebottom surface of the CEL 37 so that the reaction product is removedfrom, for example, the bottom surface of the CEL 37.

[Configuration of Shower Head 34]

FIG. 2 is an enlarged cross-sectional view illustrating an exemplaryshower head 34. The CEL 37 is provided with a bush 371 having a femalescrew formed therein. The CEL 37 is supported from the upper sidethereof by a screw 361 inserted from the upper side of the UEL base 36and fastened to the bush 371. The bush 371 and the screw 361 are formedof an insulative material. In addition, the screw 361 may be formed of aconductive material (e.g., aluminum), and the surface of the screw 361may be covered by an insulative coating (e.g., an alumite coating).

In the bottom surface of the UEL base 36, an insulating portion 366formed of an insulation material is provided on the surface where theCEL 37 is disposed. In the present exemplary embodiment, the insulatingportion 366 is an anodic oxide coating (an alumite coating) formed onthe bottom surface of the UEL base 36 by an anodic oxidation treatment.In the UEL base 36 where the CEL 37 is disposed, a plurality ofirregularities such as, for example, an opening 362 into which theinsulating member 50 and the connection member 51 are inserted, a recess363 in which a seal member such as, for example, an O-ring is disposed,a screw hole 364 into which the screw 361 is inserted, and a protrusion365, are formed as illustrated in FIG. 2, for example.

[Configuration of Conventional Plasma Processing Apparatus]

Here, descriptions will be made on a schematic configuration of aconventional plasma processing apparatus. FIG. 3 is a schematic diagramillustrating an exemplary configuration of a conventional DRM typeplasma processing apparatus. The conventional plasma processingapparatus is provided with an upper electrode 61 and a lower electrode62 on which a wafer W is mounted, within a processing container 60. ADRM 64 is disposed on the outer circumference of the processingcontainer 60. The upper electrode 61 has a dual configuration of a UELand a CEL, and the CEL is disposed to face the lower electrode 62.

The UEL and the CEL of the upper electrode 61 are grounded together. Ahigh frequency power having a predetermined frequency (e.g., 13.56 MHz)is applied to the lower electrode 62 from a high frequency power supply63. As a result, magnetron discharge occurs between the upper electrode61 and the lower electrode 62 to turn the processing gas supplied intothe processing container 60) into plasma so that a plasma processingsuch as, for example, an RIE, is performed on the wafer W placed on thelower electrode 62 by, for example, ions or radicals. In addition, areaction product produced from the processing gas is adhered to thebottom surface of the upper electrode 61.

In the plasma processing apparatus of FIG. 3, in order to remove thereaction product adhered to the CEL of the upper electrode 61, it isnecessary to take out the CEL from the processing container 60. If theCEL is taken out from the processing container 60 whenever a wafer W isprocessed, the improvement of throughput of the process is disturbed.

Thus, there is known a cleaning method using a DC superposition (DCS)method in which a negative DC voltage is applied to the upper electrode61 so as to induce either the ions or radicals generated by the plasmaof the processing gas supplied into the processing container to causethe reaction product adhered to the bottom surface of the CEL of theupper electrode 61 to react with ions or radicals to be removed.

FIG. 4 is a schematic diagram illustrating an exemplary configuration ofa DRM type plasma processing apparatus in which DCS is incorporated. Inthe DRM type plasma processing apparatus in which the DCS isincorporated, the DC power supply 66 is connected to the upper electrode61 through a filter 65. The DC power supply 66 applies a negative DCvoltage to the upper electrode 61 via the filter 65. With theconfiguration as illustrated in FIG. 4, the ions or radicals generatedby the plasma of the processing gas supplied into the processingcontainer 60 are drawn to the upper electrode 61 so that the reactionproduct adhered to the CEL of the upper electrode 61 reacts with theions or radicals to be removed.

As a result, it is enabled to remove the reaction product adhered to theCEL without taking out the CEL from the processing container 60. Forthat reason, the process throughput may be enhanced while preventingparticle pollution.

Here, the high frequency power applied from the high frequency powersupply 63 is propagated to the upper electrode 61 from the lowerelectrode 62 through the space within the processing container 60, andpropagated to the ground from the upper electrode 61. However, in theplasma processing apparatus having the configuration exemplified in FIG.4, the filter 65 is interposed between the upper electrode 61 and theground, and a voltage drop caused by, for example, an inductor, occursin the filter 65 by the high frequency power. For that reason, thepotential of the upper electrode 61 in the high frequency power ishigher than the ground voltage by the voltage drop in the filter 65 whenviewed from the lower electrode 62. For that reason, the potentialdistribution in the space within the processing container 60 isdifferent from that in the conventional plasma processing apparatusillustrated in FIG. 3.

In the case where a processing recipe has been established by finelyadjusting various parameters such as, for example, a temperature, apressure, a flow rate ratio of a processing gas, a high frequency power,and a processing time, in order to manufacture wafers W having desiredcharacteristics using the plasma processing apparatus exemplified inFIG. 3, the processing recipe, which has been used up to now, cannot beapplied when the plasma processing apparatus exemplified in FIG. 3 ismodified to the plasma processing apparatus exemplified in FIG. 4.Otherwise, even if the processing recipe, which has been used up to now,is applied, it becomes impossible to manufacture a wafer W havingcharacteristics equivalent to those of the wafers W which have beenmanufactured up to now using the plasma processing apparatus exemplifiedin FIG. 3.

Thus, in the present exemplary embodiment, the change in potentialdistribution in the space within the processing container 60 accordingto the addition of the DCS function to the configuration of the plasmaprocessing apparatus exemplified in FIG. 3 is suppressed to be low.Thus, even in the case where an adjusted previous processing recipe isused for the plasma processing apparatus having the configurationexemplified in FIG. 3, it is enabled to manufacture a wafer W havingcharacteristics equivalent to those obtained prior to adding the DCSfunction. That is, it is enabled to secure a process trace.

Configuration of Plasma Processing Apparatus 10 of Present ExemplaryEmbodiment

FIG. 5 is a schematic diagram illustrating an exemplary configuration ofa plasma processing apparatus 10 according to an exemplary embodiment ofthe present disclosure. In the plasma processing apparatus 10 of thepresent exemplary embodiment, the UEL base 36 and the CEL 37 areinsulated from each other, the UEL base 36 is grounded, a negative DCvoltage is applied to the CEL 37. In the high frequency power, the CEL37 has a potential higher than the ground potential by a voltage dropcaused by the inductor within the filter 48.

Since the UEL base 36, which is wider than the CEL 37, is connected tothe ground potential, most of the high frequency power applied from thesusceptor 12 is propagated to the ground through the UEL base 36. Thus,the CEL 37 hardly has an effect on the propagation of the high frequencypower. Thus, the potential distribution within the processing container11 in the high frequency power becomes substantially equal to that inthe configuration of FIG. 3 in which the UEL base 36 and the CEL 37 areelectrically connected with each other and grounded.

Accordingly, even if a processing recipe adjusted to be suitable for theplasma processing apparatus having the configuration exemplified in FIG.3 is used, the plasma processing apparatus 10 according to the presentexemplary embodiment enables manufacturing of a wafer W having thecharacteristics equivalent to those obtained prior to adding the DCSfunction. That is, it is enabled to secure a process trace.

[DC Voltage Range]

Next, the range of a negative DC voltage applied to the CEL 37 will bereviewed. FIG. 6 is an enlarged cross-sectional view illustrating anexemplary shape of the UEL base 6. FIG. 6 illustrates a right half ofthe UEL base 36 in FIG. 1. As illustrated in FIG. 6, the UEL base 36 isformed with, for example, an opening 362 into which the insulatingmember 50 and the connection member 51 are inserted, a recess 363 inwhich a seal member such as, for example, an O-ring, a screw hole 364into which a screw 361 is inserted, and a protrusion 365.

In the present exemplary embodiment, the insulating portion 366 formedon the bottom surface of the UEL base 36, on which the CEL 37 is placed,is, for example, an anodic oxide coating (an alumite coating). The UELbase 36 and the CEL 37 are insulated from each other by the insulatingportion 366. However, when a protruding corner rounding formed on thebottom surface of the UEL base 36 is small (when the radius of therounding is short), the insulating portion 366 may not be formed with adesired thickness in some cases. At the corner having a small rounding,the insulating portion 366 may be formed with a thin thickness. For thatreason, in the present exemplary embodiment, a rounding having a sizeequal to or larger than a predetermined value (a radius equal to orlarger than a predetermined value) is formed on a protruding cornerformed on the bottom surface of the UEL base 36.

On the bottom surface of the UEL base 36, the insulating portion 366 isformed to have a thickness of, for example, about dozens of micrometers(μm). In the present exemplary embodiment, on the bottom surface of theUEL base 36, the insulating portion 366 is formed to have a thicknessof, for example, about 50 μm. The thickness of the insulating portion366 may be in a range of 20 μm or more and 100 μm or less.

FIG. 7 is an enlarged cross-sectional view illustrating an exemplaryshape of a vicinity of an opening 362 of the UEL base 36. At the cornerbetween the opening 362 of the UEL base 36 and the bottom surface of theUEL base 36, a rounding having a sectional shape of, for example, R1.0(circular radius of 1 mm) is formed as illustrated in FIG. 7, forexample. In addition, even at the corner between the gas hole 360 of theUEL base 36 and the bottom surface of the UEL base 36, a rounding havinga sectional shape of, for example, R1.0 (circular radius of 1 mm) isformed as illustrated in FIG. 7, for example.

FIG. 8 is an enlarged cross-sectional view illustrating an exemplaryshape of a recess 363, in which a seal material is disposed. The recess363 is formed around the opening 362, for example, in a circular shapeto surround the opening 362. At the corner between the recess 363 andthe bottom surface of the UEL base 36, a rounding having a sectionalshape of, for example, R0.25 (circular radius of 0.25 mm) is formed asillustrated in FIG. 8, for example.

FIG. 9 is an enlarged cross-sectional view illustrating an exemplaryshape of a screw hole 364. At the corner between the screw hole 364 andthe bottom surface of the UEL base 36, a rounding having a sectionalshape of, for example, R1.0 (circular radius of 1 mm) is formed asillustrated in FIG. 9, for example.

FIG. 10 is an enlarged cross-sectional view illustrating an exemplaryshape of a protrusion 365 of the UEL base 36. At the corners of theprotrusion 365, a rounding having a sectional shape of, for example,R0.5 (circular radius of 0.5 mm) is formed as illustrated in FIG. 10,for example.

Next, descriptions will be made on a test result obtained by measuring awithstanding voltage in a case where an anodic oxide coating is formedas the insulating portion 366 on a surface of each of the members formedwith rounded corners as illustrated FIGS. 7 to 10. FIG. 11 is a viewillustrating an exemplary shape of a test piece 70. The test piece 70 isformed of the same material as the UEL base 36 (e.g., aluminum). On thetest piece 70, three kinds of features of a recess having a cornerrounding R0.25, a hole having a corner rounding R1.0, and a flat surfaceare formed. FIG. 11 exemplifies a test piece 70 in which a recess 71 isformed on a surface 72. The surface 72 of the test piece 70 is formedwith an anodic oxide coating having a thickness of 50 μm.

FIG. 12 is an explanatory view for describing an exemplary configurationof a test. In the test, as illustrated in FIG. 12, a member 73 formed ofthe same conductive material as the CEL 73 (e.g., silicon) was made tobe in contact with the surface 72 formed with an anodic oxide coating.In addition, the test piece 70 was grounded, the DC voltage applied tothe member 73 was increased, and a voltage of causing the initiation ofelectric discharge was measured as the withstanding voltage.

FIG. 13 is a view representing an exemplary test result of awithstanding voltage. In the test, ten (10) test pieces 70 were preparedfor each of a recess, a flat surface, and a hole, and a withstandingvoltage was measured for each of the test pieces. In the test pieces 70formed with a recess, the corner rounding between the recess and thesurface of each test piece 70 is R0.25. In addition, in the test pieces70 formed with a hole, the corner rounding between the hole and thesurface of each test piece 70 is R1.0.

As illustrated in FIG. 13, the withstanding voltages of the recesses arelow as compared to those of either the flat surfaces or the holes as awhole. It is considered that, since the radii of the corner roundingsbetween the recesses and the surfaces of the test pieces 70 are smallerthan the radii of the corner roundings between the holes and thesurfaces of the test pieces 70, the thicknesses of the anodic oxidecoatings at the corners between the recesses and the surfaces of thetest pieces 70 were thinned. The minimum value of the withstandingvoltages of the recesses was 730 V.

From the test result of FIG. 13, in the UEL base 36 having the shapeillustrated in FIG. 6, it has been found that, in the case where ananodic oxide coating having a thickness of 50 μm is provided on thesurface where the UEL base 36 is in contact with the CEL 37, and the UELbase 36 is grounded, no discharge occurs when the DC voltage is appliedto the CEL 37 is −730 V or more. For that reason, the DC voltage appliedto the CEL 37 may be −730 V or more.

[Relationship Between DC Voltage and Removal Rate of Adhered Product]

Next, a test was performed in relation to the relationship between theDC voltage applied to the CEL 37 and the removal rate of the reactionproduct adhered to the CEL 37. FIG. 14 is a view representing anexemplary test result of the removal rate of the adhered product inrelation to the DC voltage applied to the CEL 37.

As illustrated in FIG. 14, in the case where the adhered substance is,for example, aluminum (Al), when the voltage was −150 V or less, aremoval rate of 99% or more of the adhered product was obtained. Inaddition, in the case where the adhered product is hafnium (Hf), whenthe voltage was −50 V or less, a removal rate of 99% or more of theadhered product was obtained. Besides, as a result of performing thetest on the adhered product of a transition metal such as, for example,tantalum (Ta) or titanium (Ti), it has been found that, when the voltagewas −150 V or less, the removal rate of the adhered product containingthe transmission metal element is 99% or more.

Accordingly, upon considering the test result of withstanding voltage ofFIG. 13, the range of the negative DC voltage applied to the CEL 37 maybe in the range of higher than −730 V and −150 V or less. Although thetest was performed in the state where the radii of the protruding cornerroundings were in the range of R0.25 to R1.0, the radii of protrudingcorner roundings in the UEL base 36 may be R0.2 or more and R1.0 orless.

[Cleaning Sequence]

FIG. 15 is a flowchart illustrating an exemplary cleaning sequence ofthe CEL.

First, a wafer W subjected to a processing such as, for example, an RIE,is carried out from the processing container 11 (S100). Then, forexample, oxygen gas is supplied to the inside of the processing space Sfrom the gas supply source 420 through the shower head 34 (S101). Inaddition, a negative DC voltage in the range of −730 V to −150 V (e.g.,−150 V) is applied from the DC power supply 49 to the CEL 37 (S102).

Next, a high frequency power of, for example, 13.56 MHz is applied fromthe high frequency power supply 20 to the processing space S through thesusceptor 12. As a result, magnetron discharge occurs within theprocessing space S. In addition, the oxygen gas within the processingspace S is dissociated and turned into plasma so that oxygen ions oroxygen radicals are generated. Then, the bottom surface of the CEL 37 issubjected to a plasma processing by the generated oxygen ions or theoxygen radicals (S103). More specifically, the reaction product adheredto the bottom surface of the CEL 37 is removed by being decomposed bythe generated oxygen ions or oxygen radicals. In addition, when theoxygen gas is used as the processing gas, an oxide is formed on thebottom surface of the CEL 37 by the oxygen ions.

Next, the application of the negative DC voltage to the CEL 37 from theDC power supply 49 is stopped. In addition, for example, the gas of thereaction product decomposed by, for example, the oxygen ions or oxygenradicals in the processing space S is exhausted through the exhaust path13 (S104).

Next, for example, the gas of carbon tetrafluoride (CF₄) is supplied tothe inside of the processing space S from the gas supply source 420through the shower head 34 (S105). Then, a negative DC voltage in therange of −730 V to −150 V (e.g., −150 V) is applied again to the CEL 37from the DC power supply 49 (S106).

Next, a high frequency power of, for example, 13.56 MHz is applied tothe processing space S from the high frequency power supply 20 throughthe susceptor 12. As a result, magnetron discharge occurs within theprocessing space S, the CF₄ gas within the processing space S is turnedinto plasma so that fluorine ions or fluorine radicals are generated.Then, the bottom surface of the CEL 37 is subjected to a plasmaprocessing by the generated fluorine ions or fluorine radicals (S107).More specifically, the oxide formed on the bottom surface of the CEL 37is decomposed and removed by the fluorine ions or radicals.

Next, the application of the negative DC voltage to the CEL 37 from theDC power supply 49 is stopped. Then, for example, the gas of thereaction product decomposed by, for example, the fluorine ions orfluorine radicals within the processing space S is exhausted through theexhaust path 13 (S108).

In the foregoing, exemplary embodiments have been described. Accordingto the plasma processing apparatus 10 of the exemplary embodiments, aneffect according to the addition of a cleaning function to an existingplasma processing apparatus on a process may be suppressed to be low.

The present disclosure is not limited to the above-described exemplaryembodiments and a number of modifications may be made within the scopeof the present disclosure.

For example, in the above-described exemplary embodiments, although thefilter 48 is provided between the CEL 37 and the DC power supply 49, thepresent disclosure is not limited thereto. In another exemplaryembodiment, the CEL 37 and the DC power supply 49 may be connected witheach other without the filter 48 interposed therebetween. As such, sinceit is not necessary to provide the filter 48 to the plasma processingapparatus 10, the number of components of the plasma processingapparatus 10 may be reduced.

In the above-described exemplary embodiment, although the insulatingportion 366 provided between the UEL base 36 and the CEL 37 is an anodicoxide coating formed on the bottom surface of the UEL base 36, thepresent disclosure is not limited thereto. For example, a plate-shapedmember formed of an insulative material may be mounted between the UELbase 36 and the CEL 37 as the insulating portion 366. Alternatively, aninsulative film may be formed on the top surface of the CEL 37 which isin contact with the UEL base 36.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. A plasma processing apparatus comprising: aprocessing container; a gas supply source configured to supply aprocessing gas into the processing container; a placing table configuredto serve as a lower electrode and mount a processing target substratethereon; an upper electrode provided above the placing table; a highfrequency power supply configured to generate plasma of the processinggas within the processing container by applying a high frequency powerto the placing table; and a direct current (DC) power supply configuredto apply a DC voltage to the upper electrode, wherein the upperelectrode includes: (i) a base member, (ii) a cover member provided onthe base member at a side of the placing table, and (iii) an insulatingportion provided between the base member and the cover member so as toinsulate the base member and the cover member, wherein an upper portionof the base member has a larger diameter than an outermost diameter ofthe cover member such that the base member is wider and has a horizontalcross-sectional area larger than that of the cover member and isconnected directly to the ground potential, wherein the DC power supplyapplies the DC voltage to the cover member, and wherein the base memberincludes a protruding corner rounding formed on the placing table sidesurface of the base member, and a radius of the protruding cornerrounding is in a range of 0.2 mm or more and 1.0 mm or less.
 2. Theplasma processing apparatus of claim 1, wherein the insulating portionis an insulative coating formed on a surface of the base member.
 3. Theplasma processing apparatus of claim 2, wherein the base member isformed of aluminum, and the insulating portion is an anodic oxidecoating formed on the surface of the base member.
 4. The plasmaprocessing apparatus of claim 1, wherein a withstanding voltage of theinsulating portion is 730 V or less.
 5. The plasma processing apparatusof claim 4, wherein the DC power supply applies a voltage in a range ofmore than −730 V and −150 V or less to the cover member.
 6. The plasmaprocessing apparatus of claim 1, further comprising: a filter connectedbetween the cover member and the DC power supply and configured to blockhigh frequency waves.
 7. The plasma processing apparatus of claim 1,wherein a thickness of the insulating portion is in a range of 20 μm ormore and 100 μm or less.
 8. The plasma processing apparatus of claim 7,wherein the insulating portion is formed to have a thickness of about 50μm.
 9. The plasma processing apparatus of claim 1, wherein theinsulating portion is an insulative coating formed on the placing tableside surface of the base member, and the insulating portion extends overthe protruding corner rounding of the base member.
 10. The plasmaprocessing apparatus of claim 9, wherein the insulating portion is ananodic oxide coating.
 11. The plasma processing apparatus of claim 10,wherein the insulating portion has a thickness in a range of 20 μm ormore and 100 μm or less.